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Interpretive Summary: Sugarcane is one of important industrial crops worldwide. Its yield and yield components are critical for growers and scientists to evaluate and select cultivars. An experiment was conducted to investigate relationships between sugarcane canopy reflectance and yield components across 18 varieties (clones). Canopy reflectance were measured during tillering and grand growth in three crops of plant cane, first ratoon, and second ratoon. Stalk population, stalk length, stalk diameter, mean stalk weight, cane yield, commercial recoverable sugar, and sugar yield were determined at mature. The normalized difference vegetation index (NDVI) was calculated based on reflectance values in red and near infrared light. Among the yield components, stalk population and cane yield were most highly correlated with NDVI. Although the two yield parameters were highly and linearly related to NDVI measured most time in April to August, the best time of measuring canopy reflectance for yield assessment was in early grand growth. Therefore, measurements of NDVI during grand growth could be useful for predicting yield potential across clones in cultivar selection programs and used as an agronomic management tool in sugarcane production.

Technical Abstract: Sugarcane (Saccharum spp.) yield and yield components are important traits for growers and scientists to evaluate and select cultivars. Collection of these yield data would be labor intensive and time consuming in the early selection stages of sugarcane breeding cultivar development programs with a large number of clones (genotypes). A field experiment was conducted on a sand soil to investigate relationships between sugarcane canopy reflectance and yield traits, including cane yield (tonnes of cane per hectare, TCH), commercial recoverable sucrose (CRS), sucrose yield (TSH) across 18 genotypes. Canopy reflectance were measured monthly during tillering and grand growth. The number of millable stalks, stalk length, stalk diameter, mean stalk weight, TCH, CRS, and TSH were determined at mature. The normalized difference vegetation index (NDVI) was calculated based on reflectance values in red (680 nm) and near infrared (800 nm). Among the yield components, the number of stalks and TCH were most highly correlated with NDVI. Although stalk population and TCH were highly and linearly related to NDVI measured most time in April to August, the best time of measuring canopy reflectance for yield assessment across genotypes was in May (before canopy fully closure) or during early grand growth. Therefore, measurements of NDVI during sugarcane grand growth could be useful for predicting yield potential across genotypes in cultivar selection programs and used as an agronomic management tool in sugarcane production.